Field of the Invention
The present invention relates to an image forming apparatus configured to form an image on a fed recording material.
Description of the Related Art
Hitherto, an image forming apparatus such as a copying machine or a printer includes a sheet feeding tray in an apparatus main body so that copying or printing can be performed for a sheet continuously. Further, a size and a type of the sheet to be used greatly depend on an environment in which a user uses the image forming apparatus. To handle such a situation, the image forming apparatus is provided with a plurality of sheet feeding trays. On the other hand, even when the image forming apparatus includes a plurality of sheet feeding trays, there may arise a demand to temporarily execute the copying or printing for a sheet different from the sheet set on each of the sheet feeding trays. On the assumption that there may arise such a demand, the image forming apparatus also includes a manual feed tray besides the sheet feeding trays so that a desired sheet can be set with ease.
In order to feed and convey the sheet set on the manual feed tray and form an image in an appropriate position, the size of the sheet needs to be known, and it is necessary for the user to input the size of the sheet through an operation portion. In U.S. Pat. No. 5,689,759, there is proposed a configuration including a detecting unit configured to detect a sheet width so that a selectable sheet size is displayed on a display portion at a timing at which it is detected that the sheet is set on the manual feed tray, to thereby allow the user to select the sheet size. In such a related art, the size selected by the user is stored in a volatile memory or a non-volatile memory of a control portion. In such a configuration, there is no need to reset settings each time the copying or printing is performed until a detecting unit configured to detect presence of the sheet on the manual feed tray detects that there is no sheet on the manual feed tray.
In addition, the image forming apparatus has a power saving (sleep) mode function of stopping functions other than a part of functions for the purpose of power saving. In such an image forming apparatus, power consumption can be reduced by limiting the functions operating during a sleep mode to only a very limited part of functions such as a network interface (hereinafter referred to as “I/F”). In the related art, the presence of the sheet on the manual feed tray immediately before a shift is made to the sleep mode is compared with the presence of the sheet on the manual feed tray immediately after a recovery is made from the sleep mode. When it is determined that the sheet is set on the manual feed tray both at a timing of shifting to the sleep mode and at a timing of recovering therefrom, image forming processing is executed based on the sheet size stored in the non-volatile memory.
However, the related-art image forming apparatus has the following problem. Hitherto, when a shift is made to the sleep mode with the sheet being set on the manual feed tray, if the sheet set during the sleep mode is removed and a sheet having a different size is set, and then a recovery is made from the sleep mode, a detection result obtained by the detecting unit configured to detect the presence of the sheet on the manual feed tray is the same for both before and after the sleep mode, both results indicating the presence of the sheet. Therefore, also after recovering from the sleep mode, the image forming processing is executed based on size information on the sheet selected before shifting to the sleep mode.
For example, it is assumed that a shift is made to the sleep mode with a sheet having an A3 length (420 mm) being set, the A3-length sheet is removed during the sleep mode, and a sheet having an A4 length (210 mm) is set on the manual feed tray. In this case, even when the actual size of the sheet set on the manual feed tray is the A4 length, image formation is executed based on the size information of the A3 length selected before the A4-length sheet is set. Therefore, a toner image to be formed has a larger size than the size of the conveyed sheet, and toner within an area that is not to be transferred onto the sheet adheres to a member such as a secondary transfer roller. Then, the toner that has adhered to the member causes an image failure such as marking back, that is, the toner adheres to a back surface of the sheet conveyed in subsequent image forming processing. In contrast, when a change is made from the A4-length sheet to the A3-length sheet during the sleep mode, the size of the conveyed sheet (A3 length) is longer than the stored size of the sheet (A4 length), which may lead to a determination that a paper jam has occurred.